7. PROJECT SUMMARY/ABSTRACT Excessive alcohol consumption resulting in disease and increasing the risk of traumatic injury contributes significantly to the public health burden in the United States. The skeleton is a significant target organ for the deleterious effects of alcohol because it suffers alcohol-related damage in two distinct ways; both directly from excessive alcohol consumption, and indirectly due to the increased risk for traumatic injury caused by alcohol drinking behavior. Fracture nonunion is a condition where a bone fracture injury fails to heal normally requiring surgical intervention and alcohol consumption has been shown to contribute to the risk for this serious clinical complication. Currently, clinical options for patients with a non-healing fracture such as surgical grafting of autogenous or de-mineralized bone preparations each have serious limitations. Obtaining autogenous bone graft is effectively a separate surgical procedure at risk for another set complications and de-mineralized bone preparations are unreliable. Normal fracture healing is a regenerative process that utilizes stem cells to rebuild new bone at the injury site. However, we currently do not understand how alcohol affects the activity of stem cells at the fracture site. We believe that alcohol consumption negatively affects stem cell activity that is critical to successful fracture repair. The goal of this investigation is to understand if alcohol affects mesenchymal stem cell differentiation toward chondrocytes following bone fracture injury and if decreased MSC to chondrocyte differentiation may underlie alcohol related inhibition of fracture callus formation and fracture union. Because young people are more likely to suffer traumatic injury, it is important to understand the effects of episodic or binge drinking on fracture repair as binge alcohol consumption is the prevalent pattern of alcohol drinking in both adolescent and young adult populations. The fact that about 40% of the orthopaedic inpatient population is intoxicated at the time of hospital admission underscores the significance of understanding the impact of binge alcohol consumption on the fracture repair process. We believe that the data obtained from this proposal will lead to a better understanding of why alcohol consumption negatively impacts the fracture repair process and how we can improve the prognosis for orthopaedic trauma patients with bone fracture injuries complicated by concomitant alcohol consumption though the use of stem cell technology.